Flat pattern of a screw conveyor type flight?

[mschro]

Hi,

I am trying to figure out how to make a flat pattern of a screw conveyor type flight. I can model the shape exactly using a Sweep with a profile and a Helix, but I can't figure out how to make the flat pattern.

Does anyone have any suggestions?

Thanks

 

[alolesen]

I would love to here an answer for this as well. I put quite a few houers into this problem and never came up with a good solution.

 

[CorBlimeyLimey]

If the flight involves varying sheet thickness, or literal stretching (not just bending) of material, SW (& other "mid-range" 3D systems) will not be able to create a flat.


Helpful SW websites faq559-520
How to get answers to your SW questions faq559-1091

 

[mschro]

The sheet thickness is to be uniform (not varying).

Thanks

 

[CorBlimeyLimey]

I assume the flight is (basically) like a stretched spring with a rectangulr profile bent the 'wrong' way. If that is the case, in the real world (a fabrication shop) the outer edge of the rectangular profile will have to be stretched in order to wrap it around the shaft ... that involves material deformation &, currently, SW cannot process that data.

That is why SW does not allow include a sweep function within the Sheet Metal module.


Helpful SW websites faq559-520
How to get answers to your SW questions faq559-1091

 

[mschro]

Thanks for the input.

Is there an other way (other then using a sweep) to generate this shape, that would be able to create a flat pattern?

 

[smcadman]

I have to disagree with you on this one Corb. If you think about a sheet metal cone or square-to-round, you could say there is deformation or stretching of the metal involved, and this cannot be created, but we know that mathematically they actually CAN be created.

http://search.sheetmetalworld.com/tutorials.cfm

I have worked at 2 companies that fabricated chutes; one created smooth chutes, and the other created stepped chutes.

http://mooload.com/files/1131736900/SmoothChute.jpg

http://mooload.com/files/1131736992/SteppedChute.jpg

You will have he_ _ trying to find formulas for chutes, even on sheet metal fabricator forums because it is a closely-guarded secret (believe me, I have tried for hours and hours trying to get answers on this subject).

I will say that the company who made the smooth chutes had an AutoLISP routine for AutoCAD to make the flat patterns by simply entering fields in a dialog box (yeah, I know, I know, tell me again how much ACAD sucks).

I will say that the chutes can be created using trig, and it is not too far from the cone flat layout. However, Solidworks cannot flatten a helical chute.

Flores
SW06 SP1.0

 

[SBaugh]

Look at using Lofted Sheet metal.

Regards,

Scott Baugh, CSWP

http://www.scottjbaugh.com

faq731-376

 

[smcadman]

For some reason, I can't see the pics on Mooload, try these:

http://img280.imageshack.us/my.php?image=smoothchute5ey.jpg

http://img280.imageshack.us/my.php?image=steppedchute5se.jpg

Flores
SW06 SP1.0

 

[CorBlimeyLimey]

smcadman ... SW has the Lofted Bends function to handle the "chutes" you mention. Although in practice they are quite useable, I would not place too much store in the absolute accuracy of the flats produced from those, for critical applications. The deformation would be minimal & I'm guessing that SW algorithm ignores the deformation that would actually occur.

The chutes are also very different to the flights (or auger) that mschro wants. Imagine a 1/4" x 3" bar being wrapped around a shaft the "hard" way (on edge), the outer edge has to be stretched & the material thinned. Thats what I'm saying SW cannot handle.


Helpful SW websites faq559-520
How to get answers to your SW questions faq559-1091

 

[CorBlimeyLimey]

smcadman ... The MooLoad links should have been;

http://mooload.com/file.php?file=files/1131736900/SmoothChute.jpg

http://mooload.com/file.php?file=files/1131736992/SteppedChute.jpg

The chutes shown are totally different to what I was picturing. Were they made from one piece?


Helpful SW websites faq559-520
How to get answers to your SW questions faq559-1091

 

[smcadman]

The chutes are segments similar to this:

http://img190.imageshack.us/my.php?image=chutesegment7aw.jpg

but the first and last segment will vary, depending on whether the entrance and exit face north, south, east or west. They are welded together, ground smooth, then ran through a modified (tapered) slip roll. The machine is patented, but I guess I can say how it was done. After being fed through the roll, any cracks are welded, then polished smooth.

They also had an AutoLISP routine to layout the vertical edges of the chute. Actually, the formulas could be entered into EXCEL to produce a point cloud, or X-Y points to enter into SW to create the flat pattern. SW cannot flatten the swept shapes, but you can create a separate part that is the flat pattern for laser or waterjet though.

Flores
SW06 SP1.0